This invention relates to a purely mechanical lock device of the pushbutton system dispensing key and more particularly to a lock device of the type described which is of a mortise lock type.
Lock devices of the prior art generally consist of a lock body attached to one of two members to be fastened or unfastened so as to close or open them, and a key belonging to the lock body for operating the same. Some disadvantages are accompanied with the lock devices of this type of the prior art. If the user misplaces or loses his key, he will be at a loss because he is unable to unlock the locked members until the right key is found. The user may sometimes find it hard to fit the key into the keyhole at night because of darkness. The user will be unable to unlock the locked member single-handed if he wants to do so.
In this connection, lock devices are known which dispense with a key, and requirements to be met for rendering the devices operative or inoperative are set electrically or magnetically so that the order in which the pushbuttons are depressed may correspond to the key. However, lock devices of this type are not suitable for practical use because they need a power source.
A proposal has been made to use a padlock as a mechanical lock device of relatively compact size which dispenses with a key. Such padlock (Japanese Laid-Open patent application No. 55499/75) comprises two lock units and is constructed in such a manner that pushbuttons of a number r out of a total number of n are mechanically operated to meet the requirements for rendering the padlock inoperative which conform to the permutation. However, there are still a number of problems which must be solved for providing a lock device of the mortise lock type by using the lock units disclosed in this laid-open patent application. This invention provides solutions to these problems.